Hydrogen sulfide gas is nearly always present in sulphur produced during the processing of hydrocarbons. When the hydrogen sulfide gas exceeds 30 parts per million, it presents a danger to personnel of hydrocarbon processing plants. It is, therefore, desirable to degas the sulphur to remove hydrogen sulfide gas to below these levels.
The most common method for degassing sulphur involves steam sparging. In accordance with this method, steam is introduced into the liquid sulphur from below. The steam creates air bubbles which rise up through the liquid sulphur. As the air bubbles rise the volume of liquid sulphur above decreases and the surface pressure upon the air bubble decreases causing it to expand. The steam sparging method, as described, does not produce satisfactory results. The residence time in the liquid sulphur of the rapidly rising bubbles is too short and the surface area of the large bubbles is too limited to effectively release hydrogen sulfide gas from the liquid sulphur.